Treatment of cellulose acetate artificial silk



Patented Apr. 16; 1929.

UNITED STATES I 1,709,470 PATENT OFFICE.

ARCHIBALD JOHN HALL, OF TIMBERSBROOK, CONGLETON, ENGLAND, ASSIGNOR TO CELANESE CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

TREATMENT OF GELLULOSE ACETATE ARTIFICIAL SILK.

N0 Drawing. Application filed June 8, 1928, Serial No. 283,998, and in Great Britain June 8, 1926.

This invention relates to processes for the treatment of Cellulose acetate artificial silk so that it acquires permanent resistance to deterioration during treatment with hot or boiling aqueous media.

It is well known that cellulose acetate artificial silk, unlike the artificial silks of the regenerated cellulose type i. e. yiscose, cupram monium and the so-cailed nitrocellulose arti- Xo ficial silks, when subjected to the'action of moist steam, boiling water or water at a temperature exceeding about 90 C. becomes curly and woollike and sufi'ers a considerable loss of lustre. Consequently in the treat ment of yarns, fabrics and other materials containing cellulose acetate artificial silk,

steaming treatments and treatments with aqueous liquors of a temperature exceeding about 80 C. have to be avoided. This fact is somewhat disadvantageous to the use of cellulose acetate artificial silk as compared with the regenerated cellulose artificial silks,

which, as indicated above, are not in general subject to such'deterioration.

According to'the present invention cellu lose acetate artificial silk in whatever form, provided it is in the set condition, is stretched beyond its elastic limit, whereby it is rendered much more resistant to deterioration on treatment with hot aqueous media and may even retain its original lustre and not become curly and wool-like when immersed in boiling water for prolonged periods. of the stretching isentirely new technically, no process being known which renders cellulose acetate artificial silk permanently more resistant to treatment with hot aqueous media. I

It is essential that the cellulose acetate artificial silk should be in the set condition before being subjected to the stretching opera- 7 tion. In fact, if the artificial silk is not set the operation would amount to little more than the stretching which is customarilv anplied in the production of the artificial silk filaments (the so-called stretch-spinning process), and as is well known the filaments so produced under stretch are liable to the above described deterioration.

In carrying out this invention. cellulose acetate artificial silk at any stage in its production after the silk is in the set condition. is'stretched beyond its elastic limit in a dry or-wet condition for the purpose of preserving its lustre and appearance. The stretching The efiect process may be carried out after treatment with one or more softening or swelling agents for the cellulose acetate. Such softening or swelling agents Shereinafter referred to collectively as swe ling agents) may be employed in any suitable manner, for example dissolved in aqueous or organic solvents, or 1n the form of vapour, and the silk may be sub ected to their action for any suitable period of time or at any suitable temperature. Generally it is preferred to stretch the silk before removal of the swelling agent or agents although in certan instances it may be desirable to remove the swelling agent be fore or' during stretching. After stretching, the swelling agent may be removed from the yarn by Washing with Water or otherwise and the silk may then be dried in any suitable manner. I

Examples of suitable swelling agents are acetone, ethyl alcohol, "formaldehyde and g..ycerine.

The effect of stretching on the lustrdand appearance of cellulose acetate silk is largely determined by the degree of stretching. .Generally, it is found that the greater the stretchmg the greater the resistance of the resulting yarn to deterioration when immersed in boiling water, For instance,- cellulose acetate silk yarn of 3000 to 4.000 denier. wetted with water and stretched 10% in length, and afterwards immersed for 15 minutes in boiling water becomes slightly curly or wool-like and somewhat less lustrous. On the other hand, similar yarn treated for one hour at 1520 C. with a 20% aqueous solution of acetone and afterwards stretched 25% in length. does not become wool-like and retainspracti-cally the whole of its lustre when immersed for one-hour in boiling water. 7

, Accordingly, it is preferred in carrying out this invention to treat the cellulose acetate silk with a swelling agent before stretching. since this treatment causes the cellulose acetate to swell and allows the maximum strei'ch- 100 ing to be obtained without breakage or substantial breakage of the silk filaments.

This invention is not limited to the use of any special swelling agent or any limits of\ stretching beyond the elastic limit but cona sists essentially in stretching cellulose acetate silk filaments after the silk is in the fully set and finished conditionso that they have the desired resistance to deterioration in hot or boiling aqueous solution, the filaments beno I therein.

ing preferably treated before stretching with swelling agent for cellulose acetate.

.Lu is to be understood that the invention may be applied to cellulose acetate silk whether in theform of skeins, or single yarns, and when present in any manufactured fabric.

It is found that stretching of -25% in length yields satisfactory resistance to hotor boiling aqueous liquors with cellulose acetate silk yarn of 3000 to 4000 denier.

Cellulose acetate yarns of relatively high denier ma be stretched to produce yarns of lower denler and if stretched sufiiciently the resulting finer yarnswill be wholly or par- .tially resistant to deterioration when subsequently immersed in hot or boiling aqueous solutions. The yarns may be treated before stretching with suitable swelling agents.

The following examples indicate methods for carrying out this invention although it must be clearly understood that it is not limited in any way to the conditions described Example 1.

Cellulose acetate silk yarn of 3000-4000 denier is stretched 15% in length. The resulting yarn has good resistance to boiling water.

Eat-ample 2.

Cellulose acetate yarn of about 300 denier is steeped in a 15% aqueous solution of acetone for one hour at 16 C., then stretched 15% in length, washed in water for complete removal of acetone and dried. The resulting yarn withstands boiling water for at least one hour.

Example 3.

Cellulose acetate silk yarn of about 3000 denier is steeped for hour at 20 C. in 20% aqueous solution of ethyl alcohol, then stretched washed in water and dried. The resulting yarn has excellent resistance to boiling water for at least one hour.

\Vhat I claim and desire to secure by Letters Patent is 1. Process for the treatment of cellulose acetate artificial silk, comprisingstretching the artificial silk in the set condition beyond its elastic limit, whereby it is rendered more resistant to deterioration by hot aqueous media.

2. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with a swelling agent for cellulose acetate and then stretching it beyond its elastic limit, whereby it is rendered more resistant to deterioration by hot aqueous media.

3. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with a swelling agent for cellulose acetate and then stretching itbeyond its elastic limit and removing the swelling agent, whereby the artificial silk is rendered more resistant to deterioration'by hot aqueous media.

4. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with a swelling agent for cellulose acetate at ordinary temperature and then stretching it beyond its elastic limit, whereby it is rendered more resistant to deterioration by hot aqueous media.

5. Process for the treatment of cellulose acetate artificial silk, comprising treating theartificial silk in the set condition with a swelling agent for celullose acetate and then stretching it by 1525% of its length, whereby it is rendered more resistant to deterioration by hot aqueous media.

6. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with a swelling agent for cellulose acetate and then stretching it by 15-25% of its length and removing the swelling agent, whereby the artificial silk is rendered more resistant to deterioration by hot aqueous media.

7. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with an aqueous solution of acetone and then stretching it beyond its elastic limit, whereby it is rendered more resistant to deterioration by hot aqueous media.

8. Process for the treatment of cellulose acetate artificial silk, comprising treating the artificial silk in the set condition with an aqueous solution of acetone and then stretching it by 15E25% of its length, whereby it is rendered more resistant to deterioration by hot aqueous media.

In testimony whereof, I have hereunto subscribed my name.

ARCHIBALD JOHN HALL. 

